The aim of this experiment is to examine the relationship between the serotoninergic system in young male adults at risk for early onset alcoholism and impulsiveness/aggressiveness. At-risk subjects and matched controls will undergo a procedure that depletes brain levels of tryptophan, the rate limiting step in the synthesis of serotonin. We hypothesize that at-risk subjects will exhibit greater impairment on a measure of response inhibition following this manipulation compared to a placebo session and control subjects.